The invention relates to a cylindrical resistance element, and more particularly to a resistive plastic channel supported in a helical groove formed on the surface of an insulating cylinder in which a wiping contact is guided in the root of the channel.
Known prior art multi-turn conductive plastic potentiometers may be characterized as being one of two types. A precision grade of potentiometer comprises a cylindrical resistance element in which a helical screw thread has been cut through an externally disposed resistive coating to form a helical strip of resistance material. The helical strip functions as a resistance element, and the helical screw thread functions to guide a wiping contact which is disposed within the thread. A semi-precision grade of potentiometer comprises a rectilinear or flat strip resistance element and a wiper assembly which is guided by a lead screw. Using this construction, resistance ranges and conformity accuracies are limited because of the relatively short lengths which the resistance elements may not exceed in order to meet specification frame sizes.